Mercaptohydroxy alkanes

ABSTRACT

Dimercaptodihydroxy alkanes are used as a curing agent for epoxide resins and as ore flotation agents.

This invention relates to mercaptohydroxy alkanes. It specificallyrelates to dimercaptodihydroxy alkanes. It also relates to the use ofdimercaptodihydroxy alkanes as curing and flotation agents. In oneaspect this invention relates to the use of dimercaptodihydroxy alkanesas curing agents for epoxy resins. In another aspect it relates to theuse of dimercaptodihydroxy alkanes as ore flotation agents.

The methods of preparing mercaptohydroxy alkanes are known in the art.Mercaptohydroxy alkanes are produced by reacting compounds selected frommono- and poly- epoxides with about a stoichiometric amount of hydrogensulfide at temperatures of from 20° C. to 200° C. at normal to elevatedpressures in the presence of from 0.01 percent to 10 percent by weight,based on the weight of said epoxide of a strongly basic catalyst andrecovering said mercaptohydroxy alkane.

Mercaptohydroxy alkanes have been shown to be useful as insecticides andfungicides. They have also been used as emulsifiers and antioxidants.The instant invention is a novel use for dimercaptodihydroxy alkanes.Dimercaptodihydroxy alkanes have been found to be a useful curing agentfor epoxy resins and as ore flotation agents. In particular,1,10-dimercapto-2,9-dihydroxydecane has been found to be a curing agentfor epoxy resins and an ore flotation agent.

Epoxy resins are organic compounds containing at least one chemicallyreactive linkage known as an epoxy group. This group is formed by thethe union of an oxygen atom with two vicinal covalently bonded carbonatoms. When curing agents are used with epoxy resins, the resins can beformulated, through well known means in the art, into coatings,adhesives and various plastics. Most cured epoxy resins are tough, hardproducts, generally adhering tenaciously to whatever substrate it isapplied. The time required for a satisfactory cure is generally 1 to 24hours depending on the activity of both the epoxy resin and the curingagent. Curing agents, such as pentaerythritoltetra(3-mercaptopropionate) have been used with epoxy resins and arewell known in the art. One aspect of the present invention is to providea novel epoxy resin curing agent.

Another aspect is to provide a compound useful as ore flotation agents.Froth flotation is a process for concentrating minerals from ores. In afroth flotation process the ore is crushed and wet ground to obtain apulp. Additives such as collecting agents and frothing agents are addedto the pulp to assist in subsequent flotation steps and the valuableminerals are separated from the undesired gangue portions of the ore.After flotation agents are added the pulp is aerated to produce a froth.The minerals which adhere to the bubbles or froth are skimmed orotherwise removed from the surface of the flotation liquid and themineral adhering froth is collected and further processed to obtain thedesired minerals. Some minerals such as chrysocolla, a metal silicate,CuSiO₃, generally are not separated from ores by flotation but rather byacid leaching because of the difficulty in satisfactorily floating thematerial. One aspect of the present invention is to provide a flotationagent for these minerals.

Therefore, an object of this invention is to provide adimercaptodihydroxy alkane. Another object of this invention is toprovide a curing agent for epoxy resins. Another object is to provide anore flotation agent. Another object of this invention is to provide anovel compound. These and other objects will become apparent as thedescription thereof proceeds.

STATEMENT OF THE INVENTION

The instant invention provides a dimercaptodihydroxy alkane. Inparticular it provides a novel compound1,10-dimercapto-2,9-dihydroxydecane. In accordance with one embodimentof the invention, it has been found that dimercaptodihydroxy alkanes areuseful as curing agents for epoxy resins. In accordance with anotherembodiment of the invention it has been found that dimercaptodihydroxyalkanes are useful in ore flotation. In another embodiment of theinvention it relates to a process of curing epoxy resins usingdimercaptodihydroxy alkanes. In still another embodiment of theinvention it relates to a process of separating metal silicate from oresusing dimercaptodihydroxy alkanes.

The dimercaptodihydroxy alkanes suitable in this invention are of thefollowing formula: ##STR1## where n ranges from 0 to about 16, R₁ and R₂can be any alkyl radical having from 1 to 16 carbon atoms or hydrogen.The total number of carbon atoms can be from 4 to about 20. Specificexamples of dimercaptodihydroxy alkanes that can be used include1,10-dimercapto-2,9-dihydroxydecane, 1,4-dimercapto-2,3-dihydroxybutaneand 1,20-dimercapto-2,19-dihydroxyeicosane.

The instant invention is made by epoxidizing alpha, omega diolefins inany conventional manner to obtain a diepoxy alkane of the formula##STR2## where n is from 0 to about 16. R₁ and R₂ can be any alkylradical having from 1 to 16 carbon atoms or hydrogen. Examples oftypical diolefins within the scope of this invention include1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 1,4-pentadiene,1,5-hexadiene, 1,6-heptadiene, 2,4-dimethyl-1,4-pentadiene,1,7-octadiene, 1,8-nonadiene, 1,9-decadiene, 1,11-dodecadiene and1,19-eicosadiene.

The diepoxy compound thus formed is reacted with about a stoichiometricamount of hydrogen sulfide at a suitable temperature and pressure. Ingeneral, the temperature can range from about 25° C. to 125° C. and thepressure from about 0 to 20 atmospheres. The reaction takes place in thepresence of a suitable amount of a strongly basic catalyst. In general,the catalyst will be present in from about 0.01 percent to about 10percent by weight, based on the weight of the diepoxy alkane. Thestrongly basic catalyst can be any suitable catalyst. In general, thecatalyst will be selected from sodium hydroxide, potassium hydroxide andammonium hydroxide. The dimercaptodihydroxy alkanes are then separatedfrom the mixture in any conventional method.

The separated dimercaptodihydroxy alkane is then intimately mixed withan epoxy resin. This mixing may be done in any conventional manner. Themixing should continue until a homogenous mixture is achieved.

The dimercaptodihydroxy alkanes can be used in curing any epoxy, diepoxyor polyepoxy resins. In the preferred invention, the epoxy resin can bethe diglycidyl ether of bisphenol A, known commercially as EPON 828.

The dimercaptodihydroxy alkane and the epoxy resin can be combined inany ratio sufficient to effect a cure of the epoxy resin. In generalthey will be combined in a ratio from about 0.75 equivalents mercaptanper equivalent of epoxy to about 1.3 equivalents mercaptan perequivalent of epoxy resin. In the preferred embodiment of the inventionthe ratio is about 1:1 equivalents of mercaptan to an equivalent ofepoxy.

The dimercaptodihydroxy alkanes can also be used with any suitablecatalyst for curing epoxide resins. The purpose of the catalyst is toinitiate the reaction between the mercaptan groups of thedimercaptodihydroxy alkane and the epoxy groups of the epoxy resin. Inthe preferred embodiment, dimercaptodihydroxy alkanes can be used withcatalyst selected from tertiary amines such astris(dimethylaminomethyl)phenol(DMP -30), triethylamine andN,N,N',N'-tetramethylethylenediamine.

These dimercaptodihydroxy alkanes can also be used in combination withaccelerators, solvents, pigments, thickeners, fillers or any otheradditives used with epoxy resins. The dimercaptodihydroxy alkanes can beused in any epoxide application. The application areas could be, forexample, coatings, adhesives, sealants, and the like.

Dimercaptodihydroxy alkanes can also be used as ore floatation agents.In this embodiment of the invention the floatation agent is added to thecrushed and wet ground ore, known as the pulp.

The amount of flotation agent employed can vary considerably dependingupon the mineral concentration, the pH of the pulp, and the mineralbeing floated. Generally the dimercaptodihydroxy alkane flotation agentwill be used in a range from about 0.005 pounds per ton or ore or solidto about 20 pounds per ton of ore or solid.

It is generally believed that the dimercaptodihydroxy alkanes disclosedherein are useful for separating any valuable metal from itscorresponding gangue material. It is also understood that thedimercaptodihydroxy alkanes may separate a mixture of metals that arecontained in a particular mining deposit or ore, said mixture beingfurther separated by subsequent froth flotations or any otherconventional separating methods. The dimercaptodihydroxy alkanes hereindisclosed are particularly useful for separating silicate containingminerals from the total ore, such as chyrsocolla.

Other metal bearing ores within the scope of this invention are, forexample, but not limited to, such materials as:

    ______________________________________                                        Molybdenum-Bearing Ores                                                       Molybdenite       MoS.sub.2                                                   Wulfenite         PbMoO.sub.4                                                 Powellite         Ca(MoW)O.sub.4                                              Ferrimolybdite    Fe.sub.2 Mo.sub.3 O.sub.12.H.sub.2 O                        Copper-Bearing Ores                                                           Covallite         CuS                                                         Chalcocite        Cu.sub.2 S                                                  Chalcopyrite      CuFeS.sub.2                                                 Bornite           Cu.sub.5 FeS.sub.4                                          Cubanite          Cu.sub.2 SFe.sub.4 S.sub.5                                  Valerite          Cu.sub.2 Fe.sub.4 S.sub.7 or Cu.sub.3 Fe.sub.4 S.sub.7      Enargite          Cu.sub.3 (As,Sb)S.sub.4                                     Tetrahedrite      Cu.sub.3 SbS.sub.2                                          Tennanite         Cu.sub.12 As.sub.4 S.sub.13                                 Cuprite           Cu.sub.2 O                                                  Tenorite          CuO                                                         Malachite         Cu.sub.2 (OH).sub.2 CO.sub.3                                Azurite           Cu.sub.3 (OH).sub.2 CO.sub.3                                Antlerite         Cu.sub.3 SO.sub.4 (OH).sub.4                                Brochantite       Cu.sub.4 (OH).sub.6 SO.sub.4                                Atacamite         Cu.sub.2 Cl(OH).sub.3                                       Chrysocolla       CuSiO.sub.3                                                 Famatinite        Cu.sub.3 (Sb,As)S.sub.4                                     Bournonite        PbCuSbS.sub.3                                               Stannite          Cu.sub.3 FeSnS.sub.4                                        Lead-Bearing Ore                                                              Galena            PbS                                                         Antimony-Bearing Ore                                                          Stibnite          Sb.sub.2 S.sub.3                                            Zinc-Bearing Ore                                                              Sphalerite        ZnS                                                         Zincite           ZnO                                                         Smithsonite       ZnCO.sub.3                                                  Silver-Bearing Ore                                                            Argentite         Ag.sub.2 S                                                  Stephanite        Ag.sub.5 SbS.sub.4                                          Hessite           AgTe.sub.2                                                  Chromium-Bearing Ore                                                          Daubreelite       FeSCrS.sub.3                                                Chromite          FeO.Cr.sub.2 O.sub.3                                        Gold-Bearing Ore                                                              Sylvanite         AuAgTe.sub.2                                                Calaverite        AuTe                                                        Platinum-Bearing Ore                                                          Cooperite         Pt(AsS).sub.2                                               Sperrylite        PtAs.sub.2                                                  Uranium-Bearing Ore                                                           Pitchblende       U.sub.2 O.sub.5 (U.sub.3 O.sub.8)                           Gummite           UO.sub.3.nH.sub.2 O                                         ______________________________________                                    

These minerals are often associated with other valuable ores which canbe separated together from gangue or waste material during an initialflotation process or which can be separated in the initial flotationprocess by using depressants. Dimercaptodihydroxy alkanes of the presentinvention can be used with any suitable flotation depressants forseparation of valuable ores.

Any froth flotation apparatus can be used with this invention. Mostcommonly used commercial flotation machines are the Agitair (GallagherCo.), Denver (Denver Equipment Company), and the Fagergren (WesternMachinery Company). Smaller, laboratory scale apparatus, such as aHallimond cell, can also be used.

The instant invention was demonstrated in tests conducted at ambientroom temperature and at atmospheric pressure. However, any temperatureor pressure generally employed by those skilled in the art are withinthe scope of this invention.

The advantages of this invention are further illustrated by thefollowing examples.

EXAMPLE I

This example describes the preparation of the inventive compound1,10-dimercapto-2,9-dihydroxydecane from 1,9-decadiene. A solution of17.3 grams (0.13 mole) of freshly distilled 1,9decadiene and 200milliliters of methylene chloride was placed in a 1-liter round-bottomflash equipped with thermometer, stirrer and dropping funnel. Fifty-fourand one-half grams (0.27 mole) Aldrich 85 percent m-chloroperbenzoicacid in 600 milliliters methylene chloride was added dropwise to thestirred solution over about two hours keeping the temperature at 25°-30°C. with the aid of a water/ice bath. After addition of them-chloroperbenzoic acid the stirring was continued for four hours. Thesolid was filtered and washed twice with 200 milliliters of methylenechloride. The organic phases were combined, washed with 5 percent sodiumsulfite to destroy any unreacted peracid, then with 5 percent sodiumbicarbonate to remove the acid and dried over Drierite. The methylenechloride was stripped off on a rotary evaporator at room temperaturewith the aid of a vacuum pump. The product was fractionated to recover1,9-decadiene, b.p. 48° C. at 15 mmKg., 1,2-epoxy-9-decene, b.p. 84° C.at 10 mmKg., and 1,2,9,10-diepoxydecane, b.p. 88° C. at 0.5 mmKg.

Five grams of sodium hydroxide dissolved in 300 milliliters methylalcohol and 104 grams hydrogen sulfide was charged to a 1-literstainless steel reactor. The reaction mixture was heated to 65° C. and136 grams (0.80 moles) of 1,2,9,10-diepoxydecane was pumped in over a 35minute period. After the addition was complete the reaction mixture wasmaintained at 65° C. for 11/2 hours and at 93° C. for 1 hour. Thereaction mixture was cooled, excess hydrogen sulfide vented and drained.The crude reaction mixture was purged with nitrogen for 15 minutesfollowed by acidification with concentrated hydrochloric acid. Solventwas stripped on rotary evaporator using steam heat and a wateraspirator. The product was suction filtered hot and it solidified onstanding to give 162 grams of a white solid,1,10-dimercapto-2,9-dihydroxydecane.

EXAMPLE II

This example describes the evaluation of1,10-dimercapto-2,9-dihydroxydecane as a curing agent for epoxy resins.To a beaker was added 5 grams (0.0263 equivalents) of an epoxy resinEpon 828 (diglycidyl ether of bisphenol A), 3.2 grams (0.0268equivalents) of the dimercapto dihydroxy decane prepared in Example I, 3grams of methyl ethyl ketone (2-butanone) solvent and 0.25 grams ofDMP-30 catalyst, tris(2,3,6-dimethylaminomethyl)phenol. The mixture wasstirred rapidly and a thermometer immersed in the mixture to measuretemperature rise. After about 15 minutes the mixture became visibly toothick to pour, referred herein as open time. After about 30 minutes themixture became solid and was accompanied by an exotherm, the maximumtemperature reached was 90° C. (194° F.). This is the inventive run 5listed in Table I. The experiment was repeated except thedimercaptodihydroxy decane was replaced with 1,10-dimercaptodecane. Thisrun, No. 4, indicated a much slower cure rate compared to the inventiverun 5. Open time was over 2 hours. It did not become solid within 24hours nor was there any significant exotherm although it did cure butrequired a much longer time. Thus, it appears the presence of hydroxygroups is beneficial in increasing the reactivity of the mercaptan groupof the inventive compound.

Other control runs were made, Nos. 1, 2, 3, to determine curing rate ofthe epoxy resin with other curing systems. The most closely related runwas No. 2 in which another mercaptan curing agent was used, namely,pentaerythritol tetra(3-mercaptopropionate). This tetramercaptan curingagent performed comparably to the inventive dimercaptodihydroxy decane.

                  TABLE I                                                         ______________________________________                                        Effect of Epoxy Resin Curing Agents                                                        Run No.:                                                                                       In-                                                                           ven-                                                         Control          tion                                                         1   2      3        4      5                                     ______________________________________                                        A. Composition, grams                                                         1 Epon 828      5     5      5      5      5                                  2 DMP-30 (catalyst)                                                                          .25    .25    .25    .25    .25                                3 Q-43.sup.a   --    3.2    --     --     --                                  4 1,10-Dimercaptodecane                                                                      --    --     3.2    3.2    --                                  5 1,10-Dimercapto-2,9-di-                                                                    --    --     --     --     3.2                                   hydroxydecane                                                               6 MEK solvent  --    --     --      3      3                                  B. Mixing                                                                     1 Maximum Exotherm, ° C.                                                              37    110    30     31     90                                  ° F.    98    230    85     87     194                                 2 Mins. to Solid                                                                             37     27    >24 hrs.                                                                             >24 hrs.                                                                             30                                  3 Open Time, mins.                                                                           17     23    --     140    15                                  ______________________________________                                         .sup.a Pentaerythritol tetra(3mercaptopropionate) from Evans Chemetics.? 

EXAMPLE III

This example illustrates the use of the inventive compound1,10-dimercapto-2,9-dihydroxydecane as an ore flotation reagent usingthe Hallimond cell. Reasonably pure mineral, chrysocolla, was employedto more accurately measure efficiency of the collector withoutinterference from other materials such as gangue or sulfide ores. Othersimilar compounds were also tested as controls. The following is atypical procedure. To a 170 milliliter capacity Hallimond cell wascharged two grams of granulated chrysocolla, CuSiO₃, and about 69milliliters of demineralized water (pH=6.5, resistivity >1 million Ω)and the pH measured. Generally, the pH was above 7 and had to be loweredbelow 7 by the addition of dilute (10-20 percent) sulfuric acid.Additional water was added, 100 milliliters, and the mineral conditionedin the cup (70 milliliter capacity) for about 1 minute while magneticagitation was applied and maintained constant by a magnetic field,revolving at about 800 rpm. A flow of nitrogen, measured by a calibratedcapillary (F and P Co., Precision Bore Flowrator Tube No.08F-1/16-08-5136), was also maintained constant at 4 cfs. Flotation wasthen carried out for 2 minutes. The floated fractions (concentrate) werethen filtered, oven dried at 82° C. (180° F.) for 24 hours and weighed.From this weight the percent recovery of the mineral was estimated. Thisevaluation is listed in Table II where it can be seen that the inventivecompound (Run 5) floats chrysocolla, a heretofore difficult mineral tofloat. The data also show, the effectivenes of the inventive compound toact as a collector is comparable to other dimercaptans but which do notcontain the hydroxy functionality.

                  TABLE II                                                        ______________________________________                                        Effect of Dithiols as                                                         Mineral Collectors in Ore Flotation                                           (2 grams Chrysocolla-Hallimond Cell)                                                                       Wt. %                                                   Collector    lbs/Ton  Recovery                                         ______________________________________                                        Run No.                                                                       1        1,3-propanedithiol                                                                           10        0                                           2        1,2-propanedithiol                                                                           10       16                                           3        1,6-hexanedithiol                                                                            15       22                                           4        1,10-decanedithiol                                                                           10.3     20                                           Invention:                                                                    5        1,10-dimercapto-2,9-                                                                         10.3     20                                                    dihydroxydecane                                                      ______________________________________                                    

We claim:
 1. A cured composition comprising an epoxy resin anddimercaptodihydroxy alkane compounds of the formula: ##STR3## where nranges from 0 to about 16 carbon atoms; R₁ is any alkyl radical havingfrom 1 to about 16 carbon atoms or hydrogen; R₂ is any alkyl radicalhaving from 1 to about 16 carbon atoms or hydrogen; and the total numberof carbon atoms can be from 4 to about
 20. 2. A cured composition as inclaim 1 where said dimercaptodihydroxy alkane is1,10-dimercapto-2,9-dihydroxydecane.
 3. A process for effecting the cureof an epoxy resin comprising the incorporation into the resin of aneffective cure promoting amount of dimercaptodihydroxy alkane compoundsof the formula: ##STR4## where n ranges from 0 to about 16 carbon atoms;R₁ is an alkyl radical having from 1 to about 16 carbon atoms orhydrogen; R₂ is an alkyl radical having from 1 to about 16 carbon atomsor hydrogen; and the total number of carbon atoms can be from 4 to about20.
 4. A process as in claim 3 where the dimercaptodihydroxy alkane is1,10-dimercapto-2,9-dihydroxydecane.
 5. A process as in claim 3 wheresaid dimercaptodihydroxy alkanes and said epoxy resin are combined in aratio from about 0.75 equivalents mercaptan per equivalent of epoxy toabout 1.3 equivalents mercaptan per equivalent epoxy.
 6. A process as inclaim 5 where said ratio is 1.1 equivalents mercaptan per equivalent ofepoxy.
 7. A process as in claim 3 where said dimercaptodihydroxy alkaneis present with a catalyst.
 8. A process as in claim 7 where saidcatalyst is tris (dimethylaminomethyl) phenol.